DSA-4134-1 util-linux -- security update

Bjorn Bosselmann discovered that the umount bash completion from
util-linux does not properly handle embedded shell commands in a
mountpoint name. An attacker with rights to mount filesystems can take
advantage of this flaw for privilege escalation if a user (in particular
root) is tricked into using the umount completion while a specially
crafted mount is present.

For the stable distribution (stretch), this problem has been fixed in
version 2.29.2-1+deb9u1.